A flange round sight glass (also known as a flanged sight glass, circular sight window, or flanged bullseye sight glass) is a transparent viewing device designed for direct installation onto process pipelines, tanks, and vessels. It enables operators to visually inspect liquid flow, level, color, clarity, and internal conditions without opening or depressurizing the system
Typical applications include chemical processing, food and beverage production, pharmaceutical manufacturing, water treatment, and oil and gas industries—wherever reliable, real-time visual monitoring of process media is required.
Product Overview
Common Applications
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Process Pipelines: Inline flow observation for liquids, gases, and slurries; full-bore designs minimize pressure drop.
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Tanks & Vessels: Liquid level monitoring, interface detection between different fluids, and internal inspection of storage tanks and reactors.
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Industries Served: Chemical, petrochemical, pharmaceutical, food & beverage, dairy, water/wastewater treatment, pulp & paper, and general industrial processing.
Materials & Construction
A typical flange sight glass assembly consists of a metal housing (body), a glass window (lens), sealing gaskets, and fasteners. Material selection depends on operating pressure, temperature, and media compatibility.
Body / Housing Materials:
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Stainless Steel: AISI 304, 304L, 316, 316L (1.4301 / 1.4404)
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Carbon Steel: WCB, ASTM A216
Glass Window (Lens) Materials:
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Tempered Borosilicate Glass (DIN 7080): For operating temperatures up to approximately 280 °C; excellent thermal shock resistance
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Tempered Soda Lime Glass (DIN 8902): For operating temperatures up to approximately 150 °C; cost-effective standard option
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Quartz Glass: For high-temperature applications up to approximately 1000 °C
Sealing Gasket Materials:
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PTFE (FDA-compliant), EPDM, FKM (Viton®), NBR, Silicone, Graphite
Key Specifications
| Parameter | Typical Values / Options |
|---|---|
| Connection Type | Flanged (ASME B16.5, DIN EN 1092-1, DIN 28120) |
| Pressure Rating | PN6, PN10, PN16, PN25, PN40; Class 150, Class 300 |
| Nominal Sizes | DN15 (1/2″) to DN600 (24″) |
| Viewing Diameter (Glass) | Approx. 40 mm to 300 mm+ (varies by size) |
| Working Temperature | -20 °C to 300 °C (material-dependent) |
| Body Material | Stainless Steel 304/316L, Carbon Steel |
| Material | Borosilicate, Soda Lime, Quartz |
| Mounting Orientation | Horizontal or Vertical |
Advantages & Features
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Reliable Visual Monitoring: Clear, direct observation of media flow, color, and level in real time.
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Robust Flanged Connection: Securely bolts between mating flanges for a leak-tight seal; conforms to international standards (ASME B16.5, DIN EN 1092-1).
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Versatile Material Options: Stainless steel bodies for corrosive or sanitary environments; carbon steel for general industrial service. Multiple glass and gasket options to suit temperature and chemical compatibility requirements.
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Optional Accessories:
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Wiper / Scraper (for cleaning the glass from inside without disassembly)
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Integrated LED Light (for improved visibility in dark environments)
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Spray Washer (for internal cleaning of the glass)
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Mica Protection Shield (for additional thermal and chemical protection)
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Technical Specifications
| Nominal Size | Approx. Viewing Diameter (Di) | Flange Standard | Typical Pressure Rating |
|---|---|---|---|
| DN25 (1″) | ~25 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN40 |
| DN40 (1½″) | ~40 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN40 |
| DN50 (2″) | ~50 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN40 |
| DN80 (3″) | ~75 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN25 |
| DN100 (4″) | ~100 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN25 |
| DN150 (6″) | ~150 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN16 |
| DN200 (8″) | ~200 mm | DIN EN 1092-1 / ASME B16.5 | PN10–PN16 |
Note: The above dimensions are representative; exact specifications may vary based on pressure class and design configuration. Larger sizes (up to DN600) are available.
Product Documentation & Quality Assurance
Compliance & Standards
Flange round sight glasses are manufactured in accordance with applicable international standards, including but not limited to:
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Flange Standards: ASME B16.5, DIN EN 1092-1
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Glass Standards: DIN 7080 (borosilicate), DIN 8902 (soda lime)
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Design & Testing: Manufacturer-standard pressure testing; hydrostatic testing available
